Luminescence quenching of tris(4,4′-dimethyl-2,2′-bipyridyl)ruthenium(II) complex with quinones in aprotic polar medium

The photoinduced electron transfer interaction between a luminescent metal-ligand probe, [Ru(dmbpy)(3)](2+) and quinones have been investigated by absorption and fluorescence spectroscopy. The reactions of quinones with the excited state ruthenium(II) complex in DMF have been studied by luminescence quenching technique and the bimolecular quenching rate constant k(q), values are found close to the diffusion controlled rate. The complex has an absorption maximum of 458 mu. It shows a photoluminescence at 608 nm. The lifetime of the complex in DMF is 164 ns. The ground state absorption measurements are used to confirm the nature of quenching. Transient absorption spectral measurements are performed and the oxidative nature of quenching is confirmed. The detection of semiquinone anion radical using time resolved transient absorption spectroscopy and the linear variation of log k(q), vs reduction potential of the quinones confirms the electron transfer nature of the reaction.